A. P. Balachandran: Living in Physics (January 15, 1938–April 18, 2025)

A. P. Balachandran was a theoretical physicist of extraordinary versatility and originality. In a career spanning over six decades, he made many significant contributions to quantum field theory and mathematical physics. His influence extends beyond the impact of his papers, with a large number of research students and collaborators. Here, in an attempt at a coherent scientific biography, I try to contextualize and evaluate his many contributions.